Quartz oscillator plate



March 16, 1948. c. FRONDEL QUARTZ OSCILLATOR PLATE Filed Dec. 15, 1944INVENTQR CLIFFORD FRON DEL b M M1, s

ATTORNEYS Patented Mar. 16, 1948 UNITED STATES PATENT OFFICE QUARTZOSCILLATOR PLATE Clifford Frondel, Flushing, N. Y., assignor toReeves-Ely Laboratories, Inc., New York, N. Y.,

a corporation of New York Application December 15, 1944, Serial No.588,326

11 Claims. (Cl. 111-321) This invention relates to quartz oscillatorplates and has for'its object certain improvements in the method ormanufacturing oscillator plates made of quartz or equivalent material.

In the manufacture of so-called BT quartz oscillator plates, forexample, automatic or semiautomatic machines are generally employed inthe initial and intermediate states. The final finishing of the platesis, however, still largely a hand operation, the work being done byhighly skilled operatives, usually called finishers. In finishing theplates, physical dimension-s of the order of sub-millionths of an inchare involved. The finisher is usually provided with a frequencycheckingdevice, a fiat glass plate, fine abrasive, an etching solution, water, abrush, cleaning solutions, lint-free towels, a micrometer, an opticalfiat, a small square, etc.

The finisher receives the plates, sometimes called blanks, as they comefrom mechanical lapping machines, the plates having been cut tosubstantially proper length and width and usually brought close to, butless than, the desired oscillating frequency. In a plate desired to havea final frequency of, say, 8,000 kc., the machine lapping Or otherpre-hand-finishing treatment is stopped when the plate is from roughly afew hundred cycles up to ten or more kilocycles under the final desiredfrequency. A preliminary frequency check is then made by comparing thefrequency of the plate with that of a standard plate having a knownfrequency. This gives the finisher a general idea how much hand lappingthe plate should be given- To reduce the plate to its proper thickness,and hence to increase its frequency, the finisher grinds the plate in amixture of the abrasive and water on the flat glass plate, keeping thefaces of the plate as flat and parallel as possible. The plate is nextthoroughly cleaned and dried, after which its frequency is again tested.This is done by inserting the carefully cleaned plate in a holder,plugging the holder into an oscillator circuit and noting whether or notthe plate has reached the desired oscillating frequency. The lapping ofthe major plane surfaces of the plates usually is'accompanied by alapping or beveling of the edges of the plates; this operation, byremoving roughness lator-plate industry. Thus, in the so-called aciddipor etching process, the plates as obtained at the completion of themachine lapping are brought up to the desired frequency by dipping themfor the required length of time intoa solvent for quartz. This solvent,which may be, for example, hydrofluoric acid, removes quartz from thesurface of the plate and thus acts to reduce the thickness of the plateto the desired value. This process, as with hand lapping, requires anintermittent, successive, series of treatments and measurements,especially in the final stages, to ensure that the desired frequency isexactly attained. The rate of etching of different plates of the sameinitial frequency is not identical, due to variations in the cleanlinessof the surface, the roughness of the surface, and other factors, so thata uniform, timed, procedure for all plates cannot be set out. In stillanother method of finishing plates to the desired frequency, the platesare tumbled with an amount of coarse abrasive in a container until thefrequency approachesthat desired. The plates are then removed, cleaned,and are adjusted to the desired frequency either by etching or handlapping.

Alternate hand lapping, cleaning and testing are required until theplate reaches the desired frequency. The activity or the plate isdetermined by its dimensions, contour, parallelism, absence of flaws,cleanness, etc. These physical characteristics are checked, changed, andrechecked until the desired activity is obtained. The frequency of theplate changes with changes made in the plate to obtain the desiredactivity, so that the finisher must coordinate the numerous variablesgoing into the finishing operation to obtain a combination of conditionsthat yields a plate of predetermined activity and frequency.'

Hand finishing by these methods of the oscillator plates is a tedious,slow, delicate and costly operation at best and leaves much to bedesired. The human factor is an exceedingly important element in thesefinishingoperations and the results obtained tend naturally to vary fromperson to person, depending upon the particular technique employed atthe time by each finisher.

As a result of my investigation I have discovered that the frequency andcertain other characteristics of piezo-electric bodies may be addustedor varied without altering the physical dimensions of the body, such asby grinding, etching orplatlng with a metal or other material. Thefrequency of oscillation of quartz oscillator plates, for example, maybe varied continuously and this variation may be brought under continu-Masters 3 ous visual control as by an appropriate meter. This permitsthe frequency tobo adjusted exactly to a redetermined value or rangemerely by following the frequency variation on a meter and stopping thetreatment at the desired value or within the'desired range. This is notpossible in present methods of manufacture of piezoelectric bodieswhich, as noted above, involve a discontinuous alternating process ofgrinding or etching, cleaning and testing. The frequency of oscillationof quartz oscillator plates may, for example, be readily adjusted to adesired value with an accuracy up to 1 cycle or greater, dependingprimarily on the accuracy of the measuring device employed. Thisaccuracy cannot be accomplished by the conventional method ofspontaneously during radio-active disintegration.

They are (1) positively charged particles,-called alpha particles; (2)negatively charged particles, "called beta particles; and (3) unchargednoncorpuscular rays, called gamma rays. Alpha 7 particles cause intenseionization as they traverse grinding or etching because the amount ofgrinding or etching on which the change of frequency and accuracydepends cannot be accurately controlled or measured, and the change, infrequency itself cannot be observed continuously,

The frequency of a piezo-electric body that has been put into arelatively stable state by means of baking, etching with a solvent forquartz, or other treatment, such as for the purpose of eliminating orreducing spontaneous variation with time in the frequency or activity ofthe piezoelectric body, can be adjusted without destroying the stabilityof the piezo-electric body. This is not possible by present methods ofmanufacture. 39

For example, if a number of quartz oscillator plates are brought bygrinding or etching to a desired frequency, and are then baked orotherwise treated, for the purpose of stabilization, it is found thatthe frequency often changes erratically from the original value and mustthen be adjusted by additional grinding or etching. This action thendestroys the stability of the oscillator plate and the purpose of theoriginal stabilizing operation is lost. This readjustment can now beaccomplished without grinding or etching and without loss of stability.

The frequency of oscillator plates may be adjusted, for example, withoutwetting them with water or other liquids and in an entirely drycondition. Water is commonly used in the conventional method offinishing to frequency by lapping with an abrasive or-by etching, andhas been considered to contribute substantially to undesirable ageingand other phenomena in the finished oscillator plate. This difllcultymay now be obviated.

The frequency of a piezo-electric body can be adjusted while it-iscontained in its permanent holder, whether this is of the contact(pressure), air gap, wire suspension or other type of mount. If desired,the frequency of the piezo-electric body may be adjusted before itismounted in its permanent holder.

The change in frequency brought about by application of the invention isdownwards from the initial value, but the downwards change may bereversed, and the frequency restored to its original value, by suitabletreatment. The new technique is especially advantageous in the recoveryof oscillator plates that have been overshot by the ordinary methods ofhand finishing. Oscillator plates that have increased in frequency overthe upper tolerance due to ageing, or aged low activity plates that havegone overthe tolerance after cleaning to bring up the activity, may besimilarly readjusted to their original frequency.

In accordance with the invention, the method comprises the step oftreating quartz oscillator a gas; theyhave a relatively slow speed, areweakly penetrating and are readily absorbed by solids. Beta particlesare relatively high speed electrons which ionize a gas, although not sointensely as alpha particles, and are much more penetrating than alphaparticles. Gamma rays are electromagnetic rays of the same natureasx-rays but for the most part of much shorter wave length. They are verymuch more penetrating than the alpha and beta particles. They ionize agas through which they pass, the ionization being largely due to anemission of secondary beta particles which result whenever gamma raystraverse matter.

The, radium salts and the radio-active gas preparations ordinarily usedin medical work, when in radio-active equilibrium, afford all threetypes of radiation, but the glass or metal capsules used to hold theradium salt or gas preparations effectively screen of! the alphaparticles. Alpha radiation is conveniently applied by sealing the quartzoscillator plates in a container filled with radon gas, an intermediatemember of the radium disintegration series, or directly in a containerpartially filled with a radium salt. Containers having glass or metalwalls of appropriate thickness may be used to hold back both alpha andbeta particles and to permit emission of the gamma rays; so that theoscillator plates may be directly exposed to the gamma rays.

As pointed out in my co-pending application Serial No. 568,323, filedDecember 15, 1944, the change in frequency produced in oscillator platesby the radio-active emanations is downwards from the original value. Thechange is progressive and continuous during irradiation but finallyreaches a limiting value, determined by factors within the quartz,beyond which there is no further change. The rate of change appears todepend primarily on the intensity of the radiation,

but in part on variations in the properties of the quartz from specimento specimen and on pretreatment of the quartz. The continuity of thechange is of great importance from a manufacturing point of view. Thedownward direction of the change is also of particular advantage.

The downward change in frequency brought about by the radio-activeemanations is permanent under ordinary conditions, but can be reversedand the oscillator plate brought back to its original frequency bybaking at a suitably elevated temperature or by irradiating the platewith ultra-violet rays. Ultra-violet rays reverse the action of theother type of radiation. .The ability to reverse the downward change isa great advantage. In other words, the oscillator plates may be adjusteddownwards and upwards in frequency repeatedly by the proper treatment.

The rate at which the downward change in frequency of the oscillatorplates can be effected and the .total amount of change is influencedplates to the action of radio-active emanati ns 76 y the temp re a whichh qua tz is h d panying drawing. taken in conjunction with the followingdescription, in which:

Fig. 1 is a vertical cross-sectional view of a container showing aplurality of quartz oscillator plates stacked therein for treatment withradioactiv emanations; and

Fig. 2 is a vertical cross-sectional view of a similar container showinga plurality of spaced quartz oscillator plates suspended therein andconnected to a frequency meter.

Referring first to Fig. 1, the apparatus shown comprises a container lhaving a chamber i I defined by thick walls l2, preferably of lead notness than 1 /4 inches thick. A suitable removable metal rack is providedwith legs [4 fits within chamber ii, a plurality of quartz oscillatorplates l5, l5, l5, etc., being stacked therein. A plunger It extendsthrough the side wall of the container into and near the bottom ofchamber ii. The bottom of the chamber is provided with a fixed stop llagainst which a capsule l8 of radioactive material may be disposed inalignment with the plunger. The top of the container is fitted with acap is of the same thick-walled material, the cap preferably fittingtightly over the container to prevent the escape of radio-activematerial or emanations therefrom.

Referring next to Fig. 2, the apparatus shown comprises a similarcontainer !0, except that its chamber It is preferabl wide enough toaccommodate a plurality of spaced quartz oscillator plates l5. l5, l5",suspended from cap it in the manner indicated. Each oscillator plate ismounted in what amounts to a holder, or part of a holder, of thewire-support type. The ends of a pair of wires and 29 are suitablysecured to the major faces of each oscillator plate, the wires in turnbeing secured to a support or base 22 as well as being in electricalcontact with a corresponding pair of terminals 23 and 24, respectively.

Terminals 23 and 24 of the holder are insertable in and removable fromsleeves 25 and 28, respectively, within cap 19. These sleeves are, inturn, connected to a frequency meter 21 by means of leads 28 and 28. Thefrequency meter may be of conventional design having a needle 30 adaptedto move back and forth over a graduated frequency scale 3|, preferablydivided to indicate cycles per second.

In operating the apparatus of Fig. 1, a. capsule it of radio-activematerial is disposed between stop ll and the end of plunger IS. A stackof quartz oscillator plates l5, l5, I5", is fitted within rack I3, whichis then placed in position within chamber ll. Cap I9 is placed over thecontainer and plunger I6 is pushed inwardly with sufficient force tobreak capsule I8, thus permitting radio-active emanations to escapetherefrom. As the radio-active emanations diffuse throughout thecontainer, they act upon the oscillator plates. This container is usedif it is not desired to oscillate the quartz oscillator plates duringthe time of thcir irradiation.

In operating the app ratus of Fig. 2, capsule I8 is similarly placedbetween stop l1 and the end of plunger I6. Quartz oscillator plates l5,l5, l5" are suitably suspended from wires 20 and 2|, and terminals 22and 23 are pushed into contact sleeves 25 and 28, respectively. Cap l9is then placed on the container and plunger I8 is pushed inwardly tobreak capsule l8. The plates may be oscillated continuously orintermittently while exposed to the resulting radioactive emanationssothat the frequency change can be measured by means of frequencymetermoved from the container.

In accordance with the invention, quartz oscillator plates were exposedfor periods up to 37 days to radium salt preparations contained in thintubes which screened oil the alpha rays. Also, oscillator plates wereexposed for periods up to 30 days in radon gas; in this case some of theplates were so mounted in the container as to permit them to beoscillated and their frequency measured during exposure to theradiations. The oscillator plates decreased in frequency in the case ofgamma radiation, but smaller total changes were brought about by thebeta and especially the alpha radiations due to their only partialpenetration (range) into the quartz. The alpha and beta particles,however, because of their relatively great ionizing power, effect afrequency change much more rapidly than do the gamma rays. Thus, inspite of the smaller total change that they can effect, they may be moreuseful from a manufacturing point of view than the gamma radiation. Itwas found that irradiated plates gave X-ray Laue transmission patternsindistinguishable from those of non-irradiated plates.

Radon is one of the radio-active disintegration products proceeding fromuranium and radium and ultimately ends in the Ra G isotope of lead. Themembers of the disintegration series, with the exception of theend-product, lead, are unstable and'transform successively into the nextmember at definite rates. The transformation is accompanied by theemission of radiations, either alpha particles or beta particles plusamma rays. Radon itself emits only alpha particles, but the freshlyprepared gas progressively disintegrates into Ra A, Ra B, etc., allpresent simultaneously in a state of transient eqiuilibrium, and some ofthese contribute beta and gamma radiations. Because of the longhalf-life period of Ra D, 25 years, and the extremely short life of theinter-mediate disintegration products between radon and Ra D, the lengthof time in which a radon preparation can be used as a practical sourceof radiation is flirted by the disintegration constant of radon itsel Inusing radon to adjust frequency of oscillation,the plates are sealed ina hollow lead container in direct contact with the gas where they areacted upon by the alpha, beta and gamma radiations proceeding therefrom.The walls of thecontainer should be at least one inch thick to guardagainst escape of the gamma rays. Ordinarily, the-container is openedand the plates removed while a considerable portion of the originalradon charge still remains. This operatlon should be done in a' hoodunder strong ventilation. After irradiation the plates should be allowedto stand for 30 minutes or more before handling so that the activity ofthe solid radio-active decomposition products on their surface has timeto diminish to anegligible value. Care also must be taken in loading thelead container with radon. The gas is supplied in capillary glass tubesa centimeter or so long sealed within larger glass tubes which in turnare housed in a lead bottle. when removing the radon tube from the leadbottle for use, it should be handled with ions tweezers. The leadirradipermit breaking the radon tube within it after sealing. If thecapillary tube is not broken the glass walls .cut oil. the alpha andmost of the beta radiation.

The curves obtained by plotting the frequency change against time ofexposure or millicurie- 'hour exposure differ from the X-ray curves inseveral respects. The radon curves fall into two parts: an initialperiod of rapid change which comprises only part of the total frequencychange that can be effected, followed by a slow and relatively uniformchange that apparently continues to saturation. The initial rapid changeseems caused by strongly ionizing radiaaverage frequency change can becalculated directly 'ii' any one of these factors is known and if themillicurie-ur rate of change of frequency ation container should be soarranged as to different specimens of quartz. This variation,

tions of only limited penetration in quartz which Y rapidly saturate acertain thickness and thereafter are ineffective. These radiationsappear to comprise the alpha and beta particles. The

period of slow uniform change apparently represents ionization by theextremely penetrating 'but very weakly absorbed gamma radiation. It isalso found that the magnitude of the initial bump in the curve increaseswith increasing concentrationof the radon. This effect seemingly is dueto an increase in the average penetrating power of the radiation. Theincrease may arise in the shorter average path distance of the radiationin the air of the container as the radon concentration increases, withconsequent less loss of energy by absorption and scattering beforeentering the quartz.

Theoretically, the time rate of change of frequency should vary inproportion to .the concentration of ,radon, and the millicurie-hour ratewhich in the extreme cases so far encountered is about tenfold. appearsto depend primarily on a predisposing feature in the quartz itself. Theactual rate of change in frequency in a given oscillator plate varieswith the conditions of treatment, and primarily with the intensity ofradiation. The decrease in frequency during irradiation is accomplishedwith little, if any, significant change in activity.

I .An oscillator plate that has been baked at an of change in plates ofa given frequency should be constant and independent of concentration.There are'rather marked departures from this due to intrinsic variationsin the response of different specimens of quartz and to the, penetrationeffect noted above. The average millicurie-hour rate of change offrequency calculated from the limited data at hand is roughly 2.26cycles per mc.-hr. in 8163 kc. plates. The rate was calculated on thebasis of the initial, linear, pm of the frequency curves.

The advantage of the radon method is that .a large number of plates canbe equally and simultaneously. irradiated. This can be accomplished byracking the plates in the container. The unit cost is proportional tothe number of plates, since the same amount of radon will suflice forone as for many plates, within certain limits, it the gas volume is keptconstant by appropriate design of the rack and container. This is due tothe fact that only a small part of the available radiation is utilizedin any case. The principal factors that determine the application of themethod are the cost of the radon, the total number of plates to beirradiated, the average amount of frequency change desired, and the timein which the frequency change must be effected. The two latter factorsfix the amount of radon that must 'be .employed. The actual estimationof this amount requires a knowledge of the relation between radonconcentration and both the average amount of frequency change and theaverage time rate of change of frequency. These two factors are notindependent, as noted, and their relation to radon concentration varieswith the frequency of the plate. The amount of radon required, theexposure time, and the accompanying total elevated temperature is foundwhen subsequently irradiated to change frequency more rapidly. Theincrease in rate brought about by baking between 250.and 350 C. rangesup to twofold, and there isv an accompanying increase in the totalfrequency range. It is often advantageous toheat the plates to 800 to570. C. in order markedly to sensitize them prior to irradiation withX-rays. such baking has a stabilizing efiect on the irradiated plates.In this connection it may be noted that a former objection to the bakingof the plates, that of erratic increase in frequency which often broughtthe plates out of. I

tolerance, isreadily overcome by the irradiation method withoutdestroying the stability of the plates.

As previously noted, the frequency of quartz oscillator plates alsoundergoes a change when the plates are treated with ultra-violet rays;the

change in frequency, however, being upwardly instead of downwardly.Oscillator plates irradiated as described above in order to decreasetheir frequency may be reverted in frequency to their initial value whenexposed, for example, to a powerful quartz-mercury lamp. The change isaccelerated by heating the quartz oscillator plates to -l50 C. duringviolet rays.

The use of ultra-violet rays offers an imporirradiation with theultratant advantage. If for some reason the frequency of an oscillatorplate should be decreased too much 'by the other type of radiationdisclosed, its frequency may be increased to the desired value. The useof ultra-violet light rays is more particularly described and claimed inmy 00- pending application serial No. 568,330, filed December 15, 1944.

It will be clear to those skilled in this art that the invention lendsitself to numerous modifications. The oscillator plates may beirradiated whether plated or unplated, coated or uncoated. In accordancewith the invention the oscillator plates may, for example, be platedwith a metal such as gold, silver, aluminum or an alloy which may servethe purpose of making a better or more intimate electrical contact withor act as electrodes; or which may serve as protective or stabilizingfilms. The plates may, for example, be coated withamorphous silica ororganic plastic or other material which may serve the pu pose ofprotective or stabilizing films. In the case of oscillator plates thathave-been protected or stay estabiished for the plate.

9 bilized by a plating, coating or other treatment. including heatingand ageing, the radiations herein contemplated are adapted neverthelessto modify the oscillator plates so as to vary their oscillatingcharacteristics; and irradiation of the 5 plates may be conducted untiltheir frequency of oscillation reaches the desired value withoutsubstantial loss of stability. The plates may be adiusted upwards ordownwards in frequency repeatediy by use of the proper radiations.

It also is possible to adjust the plate to have a desired frequency at agiven temperature by irradiating the plate, and bringing it tofrequency, while it is held at that temperature in a suitable heating orcooling contrivance. This is not easily accomplished by the conventionallapping or etching techniques of finishing plates.

The rate of change of frequency of the plate during irradiation and alsothe total amount of frequency change that can be obtained (saturationvalue) can be modified by baking the quartz plate at a suitabletemperature before it is irradiated. Thus, baking the quartz plate at asuitably elevated temperature has been found to increase both the rateof change and the amount of change 2 of frequency over that which wouldobtain it the plate had not been baked beforehand.

The oscillator plates may be irradiated whether mounted or unmounted. Itis advantageous to irradiate the plates while they are mounted in a atemporary or permanent holder and while the plates are oscillating. Itis particularly advantageous to conduct the irradiation operation whilethe oscillator plates are mounted in a permanent holder connected with asuitable meter, so that m the change in frequency of oscillation whichtakes place may be visually observed and the ir dia tion stopped whenthe plates have attained. the desired frequency. The type of permanentholder, '1': example, may be of the pressure or clamp, air-gap, combinedpressure and air-gap, Wiresupport, mechanically or hermetically sealed,temperature-controlled or temperature protected, or the multiple-type.If the oscillator plates are mounted in a permanent holder, theradiations 4 go right through the plastic, glass or metal shell, orhousing of the holder. A suiilciently penetrating radiation must, ofcourse, be employed. This practice is especially useful in the case ofoscillator plates supported between wire suspen 5 sion mounts inthin-walled vacuum holders. If the oscillator plates are not mounted ina holder, they may be held, for example, in paper or aluminum foilenvelopes which protect them from moisture, dust and grease spots fromhandling. 5

It also is convenient under certain circumstances to irradiate a largenumber of plates simultaneously. This can be done, for example, bystacking the plates together and placing the stack directly in front ofthe window, face on. The amount of frequency change thus brought aboutis not uniform through the stack, but is greatest in the first plate,considerably less in the second, and then decreases more slowly insucceedin plates.

A further technique of irradiation that may be practiced to advantageconsists of temporarily or permanently mounting a quartz oscillatorplate within a Bakelite or other conventional holder and introducing anamount of radio-active mate- 7 rial or gas therein. The radio-activematerial is allowed to act on the quartz plate until the frequency isadjusted to the desired range or value and is then removed or flushedfrom the holder and the action thereby stopped. Alternatively. a 7

deiinite amount or radio-active material may be permanently sealedwithin the holder, to afford during the radio-active life period of thematerial the amount of radiation calculated to be necessary to reducethe frequency of the quartz plate to a desired range or value. Further,an amount of radio-active material of extremely long life. such asradium element or a salt of radium, may be permanently sealed within theholder to compensate downwards any upwards drift in frequency that mayresult from excessive heating or otherwise.

While the practice of the invention has been described with respect topiezo-electric material 15 in the form of quartz, it will also be clearto those skilled in this art that the-invention is applicable to thetreatment of other piezo-electric materials, such as Rochelle salts,tourmaline, tartrates, etc. The invention is applicable to the treatmentof any useful piezo-electric material the.frequency and oscillatingcharacteristics of which are to be varied under controlled conditions.

I claim: I

1. In the manufacture of quartz oscillator plates, the improvementwhlch'comprlses treatin; each oscillator plate with radiations from aradio-active substance adapted to decrease its frequency of oscillation.

2. In the manufacture of quartz oscillator plates, the improvement whichcomprises treatlng each oscillatorplate with radiations from aradio-active substance adapted to decrease its frequency oi oscillation,and terminating the treatment of each. plate with said radiations fromthe radio-active substance when its frequency of oscillation reaches apredetermined value.

in the manufacture of quartz oscillator plates, the improvement whichcomprises treatinc" each oscillator plate while mounted in a holderconnected to a irequency meter to the action of radiations from aradio-active substance adapted to decrease the frequency of oscillationof the plate, and terminating the treatment of each plate with saidradiations from the radio-active substance when its frequency ofoscillation reaches a predetermined value.

4. In the manufacture of quartz oscillator plates, the improvement whichcomprises treating each plate while mounted in a holder connected to afrequency meter to the action of radiations from a radio-activesubstance adapted to pass through the housing oi the holder and todecrease the frequency of oscillation of the plate, and terminating thetreatment of each plate with said radiations from the radio-activesubstance when its frequency of oscillation reaches a predeterminedvalue.

5. In the manufacture of quartz oscillator plates, the improvement whichcomprises maintaining each oscillator plate at a predeterminedtemperature, treating each plate while at said temperature withradiations from a radio-active substance adapted to decrease itsfrequency of oscillation, and terminating the treatment of the platewith said radiations from the radio-active substance when its frequencyof oscillation reaches a predetermined value.

6. In the manufacture of quartz oscillator plates, the improvement whichcomprises maintaining each oscillator plate at a predeterminedtemperature while mounted in a holder connected to a frequency meter,treating the plate while at said temperature with radiations from aradioactive substance adapted to decrease the frei1 quency ofoscillation of the late, and terminating the treatment of each platewith said radiations and to decrease the frequency of oscillation Of theplate, and terminating the treatment of each plate with said radiationsfrom the radio-active substance when its frequency of oscillationreaches a predetermined value.

' 8. In the manufacture of quartz oscillator plates, the improvementwhich comprises grinding each oscillator plate to a thickness beyondthat required to increase its frequency to a, predetermined value, andtreating each ground plate with radiations from a. radio-activesubstance adapted to decrease its frequency of oscillation.

9. In the manufacture of quartz oscillator plates, the improvement whichcomprises grinding each oscillator plate to a thickness beyond thatrequired to increase its frequency to a predetermined value, treatingeach ground plate with radiations from a radio-active substance adaptedto decrease its frequency of oscillation, and terminating the treatmentof each ground plate with said radiations from the radio-activesubstance when its frequency of oscillation reaches a predeterminedvalue. 10. In the manufacture of quartz oscillator plates, theimprovement which comprises etching each oscillator plate to a thicknessbeyond that required to increase its frequency to a predetermined value,treating each etched plate with radiations from a radio-active substanceadapted to decrease its frequency of oscillation, and terminating thetreatment of each etched plate with said radiations from theradio-active substance when its frequency of oscillation reaches apredetermined value.

11. In the manufacture of quartz oscillator plates that have beenstabilized by baking, acid washing or other treatment and that have afrequency of oscillation higher than desired, the improvement whichcomprises treating each stabilized oscillator plate with radiations froma radio-active substance adapted to decrease its frequency ofoscillation, and terminating the treatment of each stabilized plate withsaid radiations from the radio-active substance when its frequency ofoscillation reaches a predetermined value.

12. In the manufacture of quartz oscillator plates, the improvementwhich comprises treating each oscillator plate with radiations from aradio-active substance adapted to decrease its frequency of oscillation,heating each oscillator plate so treated to increase its frequency oroscillation, and terminating the heating of each plate when itsfrequency of oscillation reaches a predetermined value.

13. In the manufacture of quartz oscillator plates the improvement whichcomprises t t; ing each oscillator plate with radiations from aradio-active substance adapted to decrease its frequency of oscillation,treating each plate to the action of ultra-violet light rays adapted toincrease its frequency of oscillation, and terminating the treatment ofeach plate with said ultra-violet light rays when its frequency ofoscillation reaches a predetermined value.

14. In the manufacture of quartz oscillator plates, the improvementwhich comprises heating each oscillator plate to an elevated tempera-'ture to sensitize it to frequency change, treating each sensitized plateto the action of radiations from a radio-active substance adapted todecrease its frequency of oscillation, and terminating the treatment ofeach plate with said radiations from a radio-active substance when itsfrequency of oscillation reaches a predetermined value.

15. In the manufacture of quartz oscillator plates, the improvementwhich comprises heating each oscillator plate to an elevated temperatureto sensitize it to frequency change, treating each sensitized plate tothe action of radiations from a radio-active substance adapted todecrease its frequency of oscillation, treating each plate to the actionof ultra-violet light rays adapted to increase its frequency ofoscillation,- and terminating the treatment of each plate with saidultra-violet light rays when its frequency of 05- cillation reaches apredetermined value.

16. In the manufacture of quartz oscillator-l plates, the improvementwhich comprises heating each oscillator plate to an elevated temperatureto sensitize it to frequency change, treating each sensitized plate tothe action of radiations from a radio-active substance adapted todecrease its frequency of oscillation, heating each oscillator plate sotreated to increase its frequency of 0scillation, and terminting theheating of each.

plate when its frequency reaches a predetermined value.

17. In the manufacture of oscillator plates the step comprisingdecreasing the frequency of the oscillator plate by treating the samewith radiations from a radio-active substance.

CLIFFORD FRONDEL.

